1. Field
Embodiments relate to a semiconductor device, a light emitting device using the same, and a light emitting device package including the same.
2. Background
Group III-V compound semiconductors such as GaN are widely used in optoelectronics and the like due to wide bandgap, adjustable bandgap, and the like. Such GaN is generally grown on a sapphire substrate or a silicon carbide (SiC) substrate. However, these substrates are not suitable for large diameter application and, in particular, the SiC substrate is expensive.
FIG. 1 is a view of a general semiconductor device. Referring to FIG. 1, the semiconductor device includes a silicon substrate 5 and a GaN layer 7. To address the above-described problems, the silicon substrate 5 that is cheaper than the sapphire substrate or the SiC substrate, easily realizes large diameter and has high thermal conductivity is used. When the GaN layer 7 is disposed on the silicon substrate 5, however, lattice mismatch between GaN and silicon is very high and there is a very big difference between coefficients of thermal expansion thereof, and thus, various problems that deteriorate crystallinity, such as melt-back, cracks, pits, surface morphology defects, and the like, may occur.
For example, cracks may be caused by tensile strain occurring when the GaN layer 7 grown at high temperature is cooled. For these reasons, there is a need to develop a semiconductor device that does not cause these problems even when the silicon substrate 5 is used and has a structure capable of providing good characteristics.